Secondary air supply system for internal combustion engine

ABSTRACT

The present specification discloses a system for providing a secondary air supply to an internal combustion engine so as to reduce undesirable exhaust gases. The system includes a hose running from a region of higher pressure to the exhaust port of the engine so as to supply air to such port. The area of higher pressure preferably comes from either a forward portion of the vehicle or from a high pressure region within the clutch compartment of the engine. A one-way valve is provided adjacent the exhaust port to eliminate any back flow. The method of providing secondary air supply is also disclosed.

FIELD OF THE INVENTION

This invention relates generally to emission control systems for internal combustion engines and, more specifically, to a secondary air supply system for an engine.

BACKGROUND OF THE INVENTION

Systems have been developed to supply additional air to the hot exhaust gases of an internal combustion engine in order to reduce carbon monoxide and hydrocarbon emissions. Systems, such as that described in U.S. Pat. No. 6,382,197 to Matsumoto, employ a secondary air valve apparatus that pulls air from the air cleaner. The air is fed to the exhaust port—drawn by negative pressure created at the port when the combustion-chamber exhaust valves are closed. The additional air combined with the high temperatures present at the exhaust port helps complete combustion of unburned hydrocarbons and reacts with the carbon monoxide present to produce carbon dioxide.

The exhaust gases are emitted in pulses, controlled by the exhaust valves as spent fuel from a combustion cycle is allowed to exit the combustion chamber. The resultant pressure waves are formed as the valves open and close. During the high-pressure portion of the wave, one-way valves, such as reed valves have been used to stop reverse flow of gases in the secondary air supply system. Further, air cut-off valves are employed to prevent excessive air from entering into the exhaust gas passage.

An air supply system is also described in U.S. Pat. No. 5,590,522. An exhaust gas silencer includes suction plates to pull additional air into the exhaust gases running through the silencer. The plates are arranged against the exhaust gas flow so additional air is pulled through ports into the exhaust gas flow.

The systems employed rely on complex arrangements of valves, springs, chambers, and pipes to properly send air to the exhaust port at the right time without backfire problems. Such systems are bulky and costly and may not adequately provide a pressure differential to supply adequate air for most efficient emissions cleaning without a separate air pump or loss of power.

SUMMARY OF THE INVENTION

The present invention provides a secondary air supply to the hot exhaust of an internal combustion engine without expensive, complex control devices and bulky components. Installation on vehicles, such as all-terrain vehicles (ATVs), is simplified, effective, and inexpensive.

The present invention provides a secondary air supply system for an internal combustion engine of a vehicle. The system includes a one-way valve in fluid communication with an exhaust port of the engine. A fluid channel extends from a region of relatively high air pressure to the exhaust port of the engine. The one-way valve is coupled to the fluid channel. In one preferred embodiment of the invention, the fluid channel extends from an area of air intake at the front of the vehicle. In another preferred embodiment, the fluid channel extends from a clutch compartment of the engine.

In the first embodiment, the fluid channel comprises a hose extending from a front part of the ATV chassis, for example, forward of the engine radiator. The hose extends back to a reed valve coupled to the exhaust port of the engine. The rearward end of the hose is coupled to the reed valve. A short passage is disposed in the exhaust port running from the reed valve into a region of the exhaust gas exit from the combustion chamber. Preferably, the region of the short passage is cooled with a cooling means, such as air fins or an engine coolant fluid.

In the second preferred embodiment, the air inlet is disposed in a region of relatively high air pressure created by the clutch fan. In this embodiment, preferably, the fluid channel is created with a hose extending from the clutch compartment to the exhaust port.

A method of supplying a secondary air supply to the hot exhaust of an internal combustion engine of a vehicle is also provided. The method includes channeling air in the high-pressure region through a one-way valve to the hot exhaust gases exiting the combustion chamber of the engine. In a first preferred embodiment, the air is channeled from a forward end of the vehicle, preferably in front of an engine coolant system.

In a second preferred embodiment, the air is channeled from a clutch compartment with a clutch fan. Air is fed to the channel from the region of the clutch compartment where the clutch fan blows air creating a region of higher air pressure.

The present invention provides the advantages of simplicity and cost effectiveness. An auxiliary pump is not necessary to increase the pressure of the air that is fed to the exhaust port. The system is also small and easy to arrange in position since it is mainly comprised of a hose; the reed valve preferably being the only moving part. The secondary air supply assists the engine by creating lower emissions of noxious gases including hydrocarbons and carbon monoxide without adding significant weight or complication.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred and alternative embodiments of the present invention are described in detail below with reference to the following drawings.

FIG. 1 is a side-elevational view of an all-terrain vehicle (ATV) with the system of the present invention;

FIG. 2 is a view of the air intake system in a semi-schematic side-elevational view;

FIGS. 3 a and 3 b illustrate the connections and detail of the reed valve assembly;

FIG. 4 is a perspective view of an engine with the clutch compartment air source; and

FIG. 5 is a semi-schematic view of a secondary air supply channeled into an exhaust pipe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is ideally suited for motor vehicles such as all-terrain vehicles (ATVs) as illustrated in FIG. 1 with ATV 10. The invention, however, may be used with any internal combustion engine where cleaner emissions are desired.

All-terrain vehicle 10 includes a frame 12 holding an engine 14, wheels 16, seat 18, and handlebars 20. A conventional ATV arrangement is thus provided and used as an example herein of how the present invention may be situated for use in a vehicle application.

Engine 14 includes at least one cylinder 22, a crankcase 24, and a clutch compartment 26. Cylinder 22 is generally positioned atop crankcase 24. However, in alternate embodiments, multiple cylinders may be employed in various arrangements with crankcase 24.

The air intake system of engine 14 as shown in FIGS. 1 and 2 includes an air intake plenum 28 at the forward end of the vehicle. Plenum 28 includes an air inlet in front of a radiator 30. The air inlet of plenum 28 is at a forward portion of the vehicle for a maximum free flow of air into plenum 28. The flow of air may increase as ATV 10 is driven in a forward direction. Air from plenum 28 is directed rearwardly through a hose into air box 32. Air box 32 contains an air filter. The air is then channeled from air box 32 through another hose to carburetor 34. Alternatively, other fuel mixture devices may be used such as throttle bodies and fuel injector systems. Fuel is mixed with air and sent through a hose or a pipe to cylinder 22 for combustion therein. In the preferred embodiment of the present invention, a four-stroke engine is employed, which uses valves to allow the entrance of a fuel air mixture and to allow the exit of exhaust gases once combustion is complete. However, the present invention may alternatively be employed with a two-stroke engine.

The hot exhaust gases are allowed to exit exhaust port 36 through the side of cylinder 22. Exhaust pipe 38 is secured to the side of cylinder 22 to allow the exit of the exhaust gases from ATV 10 through muffler 40. Muffler 40 is typically mounted at a rear portion of ATV 10 such that the exhaust gases are not in the immediate vicinity of the area of the user of ATV 10.

FIG. 2 also illustrates, somewhat schematically, the connection of a secondary air hose 42 to the air inlet region of plenum 28 for channeling the secondary air supply to mix with the hot exhaust gases escaping cylinder 22. Mixture of additional air with the hot exhaust gases can more thoroughly complete the combustion of unburned hydrocarbons and also react with the carbon monoxide present to produce carbon dioxide. Thus, the gases that escape exhaust pipe 38 and muffler 40 (not shown in FIG. 2) are somewhat cleaner. An air hose inlet 46 is provided near the air inlet to plenum 28. Secondary air hose 42 extends toward exhaust port 36 to feed air into exhaust port 36. Alternatively, secondary air may be fed into exhaust pipe 38. The primary concern for effective use of the secondary air supply is to feed the air at a point where the exhaust gas temperatures are high such that more completion of combustion and combination with carbon monoxide can be driven by the high temperatures.

A one-way valve assembly 44 is connected between exhaust port 36 and secondary air hose 42. In the preferred embodiment, a reed valve assembly 44 provides a one-way valve such that hot exhaust gases do not escape into secondary air hose 42. A basic reed valve assembly may be employed comprising a stainless steel plate over an aperture. The plate is only able to open with pressure behind it such that any back pressure will close reed valve assembly 44 by pushing the stainless steel plate against the aperture that leads to secondary air hose 42.

The details of reed valve assembly 44 are illustrated in FIGS. 3 a and 3 b. Reed valve assembly 44 is secured to cylinder 22 adjacent exhaust port 36 at one end of a port passage 48 that extends from the main channel of exhaust port 36 through a wall of cylinder 22 to reed valve assembly 44. Port passage 48 is kept short to avoid condensation and provide air quickly from secondary air hose 42 and reed valve assembly 44 to enter into the stream of exhaust gases exiting exhaust port 36 into exhaust pipe 38 (not shown in FIG. 3). In a liquid-cooled engine, coolant is channeled nearby in a water jacket 49 in fluid communication with the main water jacket of cylinder 22.

Reed valve assembly 44 includes a valve body 50 having a hose connector 52 extending outwardly therefrom. Hose connector 52 is dimensioned to receive secondary air hose 42 thereon. A clamp or other fastening device is preferably employed to secure secondary air hose 42 to hose connector 52. Valve body 50 includes holes for securement fasteners 54 to extend into cylinder 22 for a secure connection between reed valve assembly 44 and exhaust port 36. A gasket or other sealing member (not shown) may be used between reed valve assembly 44 and exhaust port 36.

Hose connector 52 includes a channel that opens into a valve chamber 56. Valve chamber 56 provides space for the movement of a reed valve 58 secured to an upstream face of valve chamber 56 and positioned to cover the aperture that leads from hose connector 52 into valve chamber 56. Thus, when a positive pressure differential exists between secondary air hose 42 and valve chamber 56, reed valve 58 is allowed to open to allow air to enter valve chamber 56. However, when a negative pressure occurs, reed valve 58 is forced against the aperture to close off any backflow into secondary air hose 42. A positive pressure situation will generally occur when the engine exhaust valves are closed such that the exit of gases from the cylinder is stopped. The exhaust valves (not illustrated) thus create waves or pulses of pressure with the exhaust gases. A high-pressure situation occurs when the gases are allowed to exit exhaust port 36. In this situation, reed valve 58 experiences positive pressure such that it closes to ensure that the exhaust gases do not enter secondary air hose 42. Immediately thereafter, however, reed valve 58 opens to admit fresh air into exhaust port 36 that will mix with the next pulse of exhaust gases to exit cylinder 22.

Not only is the trough of the pressure wave of exhaust gases used to create the negative pressure differential for transfer of fresh air to exhaust port 36, the air intake of secondary air hose 42 being secured at the front of the vehicle where air is forced therein through movement of the vehicle also helps to create positive pressure.

Another preferred embodiment for supplying secondary air to the exhaust gases while creating the positive pressure in a somewhat different manner is illustrated in FIG. 4. In this preferred embodiment, secondary air hose 42 a does not extend from the front of the vehicle, but rather from a high-pressure region of clutch compartment 26. Clutch compartment 26 has fresh air therein with certain regions of higher pressure as will be explained below. In this embodiment, secondary air hose 42 a extends from a hose fitting 60 on clutch compartment 26. Hose fitting 60 is screwed or otherwise fastened to clutch compartment 26 and includes a fitting onto which secondary air hose 42 a may be secured. Secondary air hose 42 a then extends to reed valve assembly 44 for supply of fresh air thereto. Secondary air hose 42 a is preferably constructed of a Teflon ™ material with a flexible abraided stainless sheath thereabout for heat shielding protection.

Clutch compartment 26 houses a drive clutch assembly 62 and a driven clutch assembly 64 with a belt 66 between the two. Such a combination of clutch assemblies provides an automatic variable transmission for ATV 10. In this instance, it also provides a region of higher pressure within clutch compartment 26. This is due to the arrangement of drive clutch assembly 62 having an inner sheave 68 with a clutch fan 70 thereon. Clutch fan 70 includes fins on the back side of inner sheave 68 that force air outwardly from the center of inner sheave 68 to the outer perimeter thereof along an area of clutch compartment 26 for circulating air thereabout to cool belt 66 and the other components within clutch compartment 26.

Air is supplied to clutch compartment 26 with clutch air inlet 72. A hose extends from a region behind radiator 30 (not shown in FIG. 4), to supply fresh air to clutch air inlet 72 at the forward end of clutch compartment 26. A clutch air outlet 74 is provided at the other end of clutch compartment 26. Thus, as air enters clutch air inlet 72, it is circulated throughout clutch compartment 26 by clutch fan 70, which is spinning with inner sheave 68 as it is connected to the crank shaft of engine 14. The air from clutch fan 70 is driven against the region of clutch compartment 26 to which hose fitting 60 is secured. Thus, a positive pressure air supply is provided for feeding into secondary air hose 42 a.

Various alternate embodiments may be employed that do not include an automatic variable transmission. For example, a fan may be employed to create a positive pressure differential within a standard clutch compartment that does not include a belt drive setup as illustrated herein. Other alternate embodiments of positive pressure regions that include an air supply are also contemplated and fall within the scope of the present invention.

This embodiment, as illustrated in FIG. 4, provides a simplified system with very little components and only a single moving part (for a single cylinder engine). Thus, minimal maintenance is required to maintain a secondary air supply system. The system is easy to install and does not take up excess room or have excess weight to add to engine 14. No external electric pumps are required, nor are complicated valve and diaphragm systems needed. Furthermore, the air supply system does not reduce engine power.

If multiple cylinders are used, secondary air hose 42 or 42 a may simply be channeled or split to the various cylinders with a reed valve for each cylinder. The system will work with catalytic converters if necessary as the gases can all be channeled to catalytic converters after mixing with the fresh air. The system can also be used with two-stroke engines, as mentioned above. Exhaust gas pulses still exist with two-stroke engines such that the feed of fresh air into the hot gases can likewise be accomplished.

FIG. 5 illustrates another preferred embodiment of the invention with the secondary air supply entering an exhaust pipe 138. A secondary air hose 142 is in fluid communication with an air supply. The air supply may be as described above from the front of the vehicle or from another source such as the clutch compartment. However, in this embodiment a positive pressure source of air is not necessary, as the arrangement creates negative pressure at the secondary air outlet. Preferably, air hose 142 channels air through a valve assembly 144 and an air channel 143. Air channel 143 feeds air into exhaust pipe 138 with the end of the channel open to the interior of exhaust pipe 138. Thus, hot, escaping gases rushing past the end of channel 143 create a low pressure region (venture effect) to pull additional air into the exhaust stream.

While the preferred embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the the preferred embodiment. Instead, the invention should be determined entirely to the claims that follow. 

1. A secondary air supply system for an internal combustion engine of a vehicle comprising: a. a one-way valve in fluid communication with an exhaust port of the engine; and b. a fluid channel extending from a region of relatively high air pressure at the front of the vehicle to the exhaust port of the engine; said one-way valve being coupled to said fluid channel.
 2. The system of claim 1, wherein said fluid channel comprises a hose extending from forward of a radiator of the engine.
 3. The system of claim 2, wherein said one-way valve comprises a reed valve.
 4. The system of claim 1, wherein said one-way valve is coupled to the exhaust port of the engine, said fluid channel having a rearward end being coupled to said one-way valve.
 5. The system of claim 1, wherein a short passage is disposed in the exhaust port running from said one-way valve into a region of exhaust gas exit from the combustion chamber.
 6. The system of claim 5, wherein a region of said short passage is cooled with an engine coolant.
 7. A secondary air supply system for an internal combustion engine having a clutch compartment with a clutch and a clutch fan, the system comprising: a. a fluid channel extending from the clutch compartment to an exhaust port of the combustion chamber of the engine; and b. a one-way valve in fluid communication with said fluid channel.
 8. The system of claim 7, wherein said fluid channel includes an air inlet in a region of relatively high air pressure created by the clutch fan.
 9. The system of claim 8, wherein said fluid channel is created with a hose extending from the clutch compartment to the exhaust port.
 10. The system of claim 8, wherein said one-way valve comprises a reed valve coupled to the exhaust port.
 11. The system of claim 7, wherein a short passage is disposed in the exhaust port running from said one-way valve.
 12. The system of claim 1 1, wherein said short passage is cooled with engine coolant.
 13. A method of supplying a secondary air supply to the hot exhaust of an internal combustion engine of a vehicle comprising channeling air from a forward end of said vehicle at a region of relatively high air pressure through a one-way valve to the hot exhaust gases exiting the combustion chamber of the engine.
 14. The method of claim 13, wherein the air is channeled from a location in front of an engine coolant system.
 15. The method of claim 14, wherein the air is channeled to a reed valve coupled to an exhaust port of the engine.
 16. A method of supplying a secondary air supply to the hot exhaust gases of an internal combustion engine having a clutch compartment with a clutch fan, the method comprising channeling air from the clutch compartment, through a one-way valve, to an exhaust port of the engine, wherein the air channeled from the clutch compartment is from a region of relatively high pressure compared to the pressure at the exhaust port of the engine between exhaust pulses.
 17. The method of claim 16, wherein air is fed to the channel from a region of the clutch compartment where the clutch fan blows air, creating a region of higher air pressure. 